Nanofibers are applied to the fields demanding optical characteristics such as high transparency, where the nano-size effect of nanofibers are taken advantage of. For example, nanofibers with a diameter equal to or below the wavelength of visible light provide transparent fabric. By the use of nanofibers the diameter of which is equal to the wavelength of visible light, structural color may be exhibited. Nanofibers have also been studied for their applicability to the fields demanding superabsorbent characteristics or high surface activity, where the high specific surface area effect of nanofibers is taken advantage of, and to the fields demanding mechanical characteristics such as tensile strength and electrical characteristics such as high conductivity, where the supramolecular arrangement effect of nanofibers is made use of Nanofibers having such characteristics have been used in the form of, for example, not only single fibers but aggregates (i.e., fabrics) or composites.
Applications of nanofibers that have been proposed include a cosmetic sheet comprising a network structure made of a water soluble polymer nanofiber and a cosmetic or a cosmetic component, such as ascorbic acid, held in the network structure as disclosed in patent literature 1 below. According to the disclosure, the cosmetic sheet is obtained by electrospinning a liquid prepared by mixing a cosmetic or a cosmetic component into a solution of a polymer dissolved in water or a solvent. The cosmetic sheet obtained by this method contains the cosmetic or cosmetic component inside the nanofiber. The literature alleges that the cosmetic sheet has not only improved adhesion or comfort to the user's face, hand, or leg but also storage stability.
Patent literature 1 also teaches incorporating particles into a nanofiber sheet. Incorporating particles in a nanofiber sheet is also described in Patent literatures 2 to 4 below. In this regard, patent literature 1 proposes a cosmetic sheet comprising a network structure formed of polymer-based nanofibers and metal particles as a cosmetic component supported by the network structure. Patent literature 2 describes incorporating particles of, e.g., kaolin, carbon black, titanium oxide, or talc into a nanofiber sheet. Patent literature 3 also describes a nanofiber sheet containing a pigment.